gcc/ada/s-tpobop.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS               --
   4 --                                                                          --
   5 --    S Y S T E M . T A S K I N G . P R O T E C T E D _ O B J E C T S .     --
   6 --                            O P E R A T I O N S                           --
   7 --                                                                          --
   8 --                                  S p e c                                 --
   9 --                                                                          --
  10 --          Copyright (C) 1992-2001, Free Software Foundation, Inc.         --
  11 --                                                                          --
  12 -- GNARL is free software; you can  redistribute it  and/or modify it under --
  13 -- terms of the  GNU General Public License as published  by the Free Soft- --
  14 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  15 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
  16 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  17 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  18 -- for  more details.  You should have  received  a copy of the GNU General --
  19 -- Public License  distributed with GNARL; see file COPYING.  If not, write --
  20 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  21 -- MA 02111-1307, USA.                                                      --
  22 --                                                                          --
  23 -- As a special exception,  if other files  instantiate  generics from this --
  24 -- unit, or you link  this unit with other files  to produce an executable, --
  25 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  26 -- covered  by the  GNU  General  Public  License.  This exception does not --
  27 -- however invalidate  any other reasons why  the executable file  might be --
  28 -- covered by the  GNU Public License.                                      --
  29 --                                                                          --
  30 -- GNARL was developed by the GNARL team at Florida State University.       --
  31 -- Extensive contributions were provided by Ada Core Technologies, Inc.     --
  32 --                                                                          --
  33 ------------------------------------------------------------------------------
  34
  35 --  This package contains all the extended primitives related to
  36 --  Protected_Objects with entries.
  37 --  The handling of protected objects with no entries is done in
  38 --  System.Tasking.Protected_Objects, the simple routines for protected
  39 --  objects with entries in System.Tasking.Protected_Objects.Entries.
  40 --  The split between Entries and Operations is needed to break circular
  41 --  dependencies inside the run time.
  42
  43 --  Note: the compiler generates direct calls to this interface, via Rtsfind.
  44 --  Any changes to this interface may require corresponding compiler changes.
  45
  46 with Ada.Exceptions;
  47 --  used for Exception_Id
  48
  49 with System.Tasking.Protected_Objects.Entries;
  50
  51 package System.Tasking.Protected_Objects.Operations is
  52    pragma Elaborate_Body;
  53
  54    type Communication_Block is private;
  55    --  Objects of this type are passed between GNARL calls to allow RTS
  56    --  information to be preserved.
  57
  58    procedure Protected_Entry_Call
  59      (Object             : Entries.Protection_Entries_Access;
  60       E                  : Protected_Entry_Index;
  61       Uninterpreted_Data : System.Address;
  62       Mode               : Call_Modes;
  63       Block              : out Communication_Block);
  64    --  Make a protected entry call to the specified object.
  65    --  Pend a protected entry call on the protected object represented
  66    --  by Object. A pended call is not queued; it may be executed immediately
  67    --  or queued, depending on the state of the entry barrier.
  68    --
  69    --    E
  70    --      The index representing the entry to be called.
  71    --
  72    --    Uninterpreted_Data
  73    --      This will be returned by Next_Entry_Call when this call is serviced.
  74    --      It can be used by the compiler to pass information between the
  75    --      caller and the server, in particular entry parameters.
  76    --
  77    --    Mode
  78    --      The kind of call to be pended
  79    --
  80    --    Block
  81    --      Information passed between runtime calls by the compiler
  82
  83    procedure Timed_Protected_Entry_Call
  84      (Object                : Entries.Protection_Entries_Access;
  85       E                     : Protected_Entry_Index;
  86       Uninterpreted_Data    : System.Address;
  87       Timeout               : Duration;
  88       Mode                  : Delay_Modes;
  89       Entry_Call_Successful : out Boolean);
  90       --  Same as the Protected_Entry_Call but with time-out specified.
  91       --  This routines is used when we do not use ATC mechanism to implement
  92       --  timed entry calls.
  93
  94    procedure Service_Entries (Object : Entries.Protection_Entries_Access);
  95    pragma Inline (Service_Entries);
  96
  97    procedure PO_Service_Entries
  98      (Self_ID : Task_ID;
  99       Object  : Entries.Protection_Entries_Access);
 100    --  Service all entry queues of the specified object, executing the
 101    --  corresponding bodies of any queued entry calls that are waiting
 102    --  on True barriers. This is used when the state of a protected
 103    --  object may have changed, in particular after the execution of
 104    --  the statement sequence of a protected procedure.
 105    --  Note that servicing an entry may change the value of one or more
 106    --  barriers, so this routine keeps checking barriers until all of
 107    --  them are closed.
 108    --
 109    --  This must be called with abortion deferred and with the corresponding
 110    --  object locked.
 111
 112    procedure Complete_Entry_Body (Object : Entries.Protection_Entries_Access);
 113    --  Called from within an entry body procedure, indicates that the
 114    --  corresponding entry call has been serviced.
 115
 116    procedure Exceptional_Complete_Entry_Body
 117      (Object : Entries.Protection_Entries_Access;
 118       Ex     : Ada.Exceptions.Exception_Id);
 119    --  Perform all of the functions of Complete_Entry_Body. In addition,
 120    --  report in Ex the exception whose propagation terminated the entry
 121    --  body to the runtime system.
 122
 123    procedure Cancel_Protected_Entry_Call (Block : in out Communication_Block);
 124    --  Attempt to cancel the most recent protected entry call. If the call is
 125    --  not queued abortably, wait until it is or until it has completed.
 126    --  If the call is actually cancelled, the called object will be
 127    --  locked on return from this call. Get_Cancelled (Block) can be
 128    --  used to determine if the cancellation took place; there
 129    --  may be entries needing service in this case.
 130    --
 131    --  Block passes information between this and other runtime calls.
 132
 133    function Enqueued (Block : Communication_Block) return Boolean;
 134    --  Returns True if the Protected_Entry_Call which returned the
 135    --  specified Block object was queued; False otherwise.
 136
 137    function Cancelled (Block : Communication_Block) return Boolean;
 138    --  Returns True if the Protected_Entry_Call which returned the
 139    --  specified Block object was cancelled, False otherwise.
 140
 141    procedure Requeue_Protected_Entry
 142      (Object     : Entries.Protection_Entries_Access;
 143       New_Object : Entries.Protection_Entries_Access;
 144       E          : Protected_Entry_Index;
 145       With_Abort : Boolean);
 146    --  If Object = New_Object, queue the protected entry call on Object
 147    --   currently being serviced on the queue corresponding to the entry
 148    --   represented by E.
 149    --
 150    --  If Object /= New_Object, transfer the call to New_Object.E,
 151    --   executing or queuing it as appropriate.
 152    --
 153    --  With_Abort---True if the call is to be queued abortably, false
 154    --   otherwise.
 155
 156    procedure Requeue_Task_To_Protected_Entry
 157      (New_Object : Entries.Protection_Entries_Access;
 158       E          : Protected_Entry_Index;
 159       With_Abort : Boolean);
 160    --  Transfer task entry call currently being serviced to entry E
 161    --   on New_Object.
 162    --
 163    --  With_Abort---True if the call is to be queued abortably, false
 164    --   otherwise.
 165
 166    function Protected_Count
 167      (Object : Entries.Protection_Entries'Class;
 168       E      : Protected_Entry_Index)
 169       return   Natural;
 170    --  Return the number of entry calls to E on Object.
 171
 172    function Protected_Entry_Caller
 173      (Object : Entries.Protection_Entries'Class) return Task_ID;
 174    --  Return value of E'Caller, where E is the protected entry currently
 175    --  being handled. This will only work if called from within an entry
 176    --  body, as required by the LRM (C.7.1(14)).
 177
 178    --  For internal use only:
 179
 180    procedure PO_Do_Or_Queue
 181      (Self_ID    : Task_ID;
 182       Object     : Entries.Protection_Entries_Access;
 183       Entry_Call : Entry_Call_Link;
 184       With_Abort : Boolean);
 185    --  This procedure either executes or queues an entry call, depending
 186    --  on the status of the corresponding barrier. It assumes that abortion
 187    --  is deferred and that the specified object is locked.
 188
 189 private
 190    type Communication_Block is record
 191       Self      : Task_ID;
 192       Enqueued  : Boolean := True;
 193       Cancelled : Boolean := False;
 194    end record;
 195    pragma Volatile (Communication_Block);
 196
 197    --  ?????
 198    --  The Communication_Block seems to be a relic.
 199    --  At the moment, the compiler seems to be generating
 200    --  unnecessary conditional code based on this block.
 201    --  See the code generated for async. select with task entry
 202    --  call for another way of solving this.
 203
 204 end System.Tasking.Protected_Objects.Operations;